3.3.9 Dermatofibrosarcoma protuberans
Grading & Level of Importance: C
Rare tumor, but on the skin the most frequent sarcoma type, panethnic, 1:100.000/ year, male:female ratio 1:1,5, mean age around 40 years. Children mostly not affected.
Dermatofibrosacoma protuberans ( DFSP) is a rare usually non metastizing mesenchymal malignant tumor with an undermining-infiltrative ,aggressive growth pattern and high local recurrence rate.
Aetiology & Pathogenesis
The cause of DFSP is unknown, but a traumatic initiation is discussed. A trauma has been reported in about 10-20% of cases. In 90 % of cases a translocation of genetic material 17q22; 22q13 with fusion of genes COL1A1 and PDGFß has been detected. The gen product, a COL1A1-PDGFß- fusion protein binds to a constitutive expressed PDGF-receptor acting thereafter as an autocrine growth stimulus for DFSP-cells. It usually does not metastasize (< 1%), however, it is highly agressively growing horizontally in the sorrounding , therefore classified as G2.
Signs & Symptoms
DFSP arises from deeper layers of the dermis. Typically, at the beginning no subjective symptoms are reported. DFSP appears solitary and starts starts as a small, firm skin coloured patch and may turn into purplish, reddish, or flesh-colored and is usually without clear margins. A rare variant is pigmented. The tumor grows slowly and infiltrative horizontally and polycyclic but becomes later a plaque and /orclassical derma a big node. At late stage it can exulcerate.
It is commonly found on the trunc, usually in the shoulder and chest area.
Dermatofibrosarcoma protuberans, cassical type.
Bednar-tumor, pigmented type.
Pleomorphic – storiform type.
Laboratory & other workups
The biopsy is essential to diagnose the tumor. For the diagnosis one needs a representative tart piece like biopsy, a punch biopsy is usually less helpful. By low power magnification one can see a the whole dermis infiltrating mesenchymal tumor composed of bundles of spindle cells. A fascicular and radiary growth produces the typical cartwheel pattern. Infiltrating the subcutis produces a honey comb pattern with large bundles of tumor cells sorrounding the adipose cells. By immunohistochemistry the tumor cells express the CD 34 antigen.
A regular follow-up is essential after tumor removal to monitor for recurrence. Local relapses appear in 10-20% of DFSP`s, usually within three years of the initial surgery. Despite being locally aggressive, the tumor spreads to other parts of the body (metastasizes) in only 5% of cases.
Infiltration with joint involement, exulceration. Scarring.
Diagnosis relies on clinical features and dermpathology.
Prevention & Therapy
Treatment depends on size and localization. Typically, it is treated with complete wide surgical excision of > 3 cm (lowest recurrence rate of 7%); Mohs surgery or 24 hrs dermpath finding is performed dependent on localisation.
The chemotherapeutic agent imatinib mesylate is approved for adults with unresectable, recurrent, or metastatic dermatofibrosarcoma protuberans.
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